PS11-22. Evaluation of Plant Maturity and Inoculum on Silage Produced from Leguminous Beans.

Abstract

As weather patterns change and water resources become more sparse, it is necessary to systematically evaluate alternative drought-tolerant crops. These alternatives are essential to provide consistent high-quality forage for cattle production. Tepary bean (Phaseolus acutifolius) is a drought and heat tolerant annual legume native to northwestern Mexico and the southwestern United States. Tepary yields similar forage biomass and N quality as soybeans (Glycine max) however it grows as a bushy semi-vine canopy. To evaluate tepary as an ensiled forage source, we harvested tepary and soybean biomass from 3 replicate fields at reproductive stages 4, 5 or 6 and treated chopped forage material with either water (control), lactic acid bacteria (LAB), molasses or LAB & molasses and ensiled the material for 50 d in plastic bags. Tepary silage had increased concentrations of neutral and acid detergent fiber (P < 0.01) compared to soybean silage. Measures of fiber were greater (P < 0.01) at reproductive stage 5 compared to 4 or 6. Addition of molasses only decreased (P < 0.01) concentrations of fiber in ensiled material compared to control and LAB. Silage pH was greater (P < 0.01) among samples from reproductive stage 5 and 6 compared to 4 and the pH of soybean silage was greater (P < 0.01) than from tepary. Addition of molasses decreased (P < 0.01) pH by 6% compared to control or LAB while LAB & molasses was intermediate. There was no effect of the interaction between species and stage (P = 0.38) or species and treatment (P = 0.23) on pH. Plant species did not effect (P = 0.54) dry matter (DM) recovery, however greater (P < 0.01) DM remained after ensiling at reproductive stage 4 compared to 6. Treatment of biomass with LAB or LAB & molasses decreased (P < 0.01) DM recovery after ensiling. Measures of in situ DM that were immediately soluble were greater in tepary (P < 0.01) and silage harvested at reproductive stage 4 (P < 0.01). Amounts of undegradable DM were greater (P < 0.01) in tepary and greatest (P < 0.01) among silage harvested at reproductive stage 5 and least from stage 4. Effective DM degradation was greater (P < 0.01) in soybean and greatest (P < 0.01) from reproductive stage 4, 6 was intermediate and while stage 5 had the least amount of DM degradation. Addition of molasses increased DM degradation, control and LAB & molasses were intermediate, while treatment with LAB had the least DM degradation. Data from this study indicates that DM digestion is decreased in tepary silage compared to soybean which may be in response to increased fiber content. Treatment of forage biomass prior to ensiling did not obviate species differences in nutrient quality.